Prestressed concrete products are traditionally prepared on long, mobile prestressing beds. Thereby, all production machines move along the casting beds, whereby their work area is very large. The concrete must be transferred to mobile casting machines in various parts of the production area, whereafter the fresh concrete is fed to moulds while the machines move across the mould. After hardening, the prestressing wires are cut, and the necessary cutting and boring operations are carried out in situ. The products are transferred to a store, and after cleaning, the prestressing wires can be fitted on the casting beds for the next casting.
A so-called carousel production system is known for short products, in which instead of fixed casting beds and mobile machines, mobile moulds and fixed casting and other work-stations are used. Said system is more flexible than the system with fixed casting beds, but when long prestressed products, or several elongated prestressed products are to be produced in series on the same casting bed, the hardening stage will slow down the production, because the filled moulds are to be left alone for a long time before the hardened product can be removed. From patent application GB 9607158.4 a plant for the production of prestressed concrete products is known, in which the concrete products are cast on beds provided with tensioning wires, while said beds move under the stationary casting machine. After the whole length of the product is cast, the whole product is pushed sideways in a heated hardening space. After hardening, the whole product passes through a sawing station in the direction opposite to the casting direction. The products, cut to their final length, are lifted from the bed and brought out of the circulation, after which the casting bed is transferred to a furnishing station by pushing sideways, cleaned and furnished for the next casting.
Said publication GB 9607157.4 discloses five parallel stations for the hardening stage, which arrangement is in harmony with the unloading and equipment stations of the other side of the circulation, but which considerably limits the amount of castings being at the same time in the hardening stage.